β-Cyclodextrin cation exchange polymer membrane for improved second-generation glucose biosensors

Both condensation β-cyclodextrin polymer (β-CDP) and condensation carboxymethylated β-cyclodextrin polymer (β-CDPA) were used for preparation of membranes for amperometric glucose biosensors. Glucose oxidase (GOD) was covalently immobilized in the membranes and the tetrathiafulvalenium/tetrathiafulvalene (TTF+/TTF) mediating couple was retained in the β-CDP membrane due to supramolecular complex formation while in the β-CDPA one due to supramolecular complex formation as well as ion exchange (by the pending carboxymethyl groups). In the latter case, retention of the mediator was greatly improved, leading to a superior biosensor performance. This performance was tested in phosphate buffer pH 7.4 with respect to the optimum GOD and TTF loadings as well as the membrane thickness. Under the optimum conditions, i.e., at the 90 units GOD and 0.1 mg TTF loadings and ca. 45 μm membrane thickness, the electrode detectability, sensitivity and response time towards glucose were 0.2 mM, 2.54 μA ml−1 and 25.5 s, respectively. The (β-CDPA)-GOD-TTF biosensor displays excellent selectivity towards glucose in the presence of commonly interfering substances, such as ascorbic acid, uric acid and acetaminophen. The (β-CDPA)-GOD-TTF preparation strategy was employed for fabrication of glucose biosensors based on a disposable screen-printed Ag-carbon strip two-electrode transducer.